make libvirt package and service optional

add two parameters:
install_libvirt: if set to false, libvirt package is not installed
establish_libvirt_service: if set to false, the libvirt service
is not created.
In both cases, you have to met dependencies yourself in your own
manifest (eg. use module puppetlabs-libvirt).

Change-Id: I0a005f8e5a59ea95219d9f6c8d5f262bc9408bcf

manifests/compute/libvirt.pp

@@ -61,6 +61,20 @@
 #   how many seconds it will be removed.
 #   Defaults to undef
 #
+# [*establish_libvirt_service*]
+#   (optional) if set to false, this class does not define
+#   the libvirt service. You need to define the service
+#   yourself eg. in an other class to match dependencies
+#   (Service['libvirt']).
+#   Defaults to true (= establish service).
+#
+# [*install_libvirt*]
+#   (optional) if set to false the libvirt package is not
+#   installed. You need to install the libvirt package
+#   yourself (e.g. in an other class) and ensure
+#   dependencies (Package['libvirt']).
+#   Defaults to true (install package).
+#
 
 class nova::compute::libvirt (
   $libvirt_virt_type                          = 'kvm',
@@ -72,6 +86,8 @@ class nova::compute::libvirt (
   $remove_unused_kernels                      = undef,
   $remove_unused_resized_minimum_age_seconds  = undef,
   $remove_unused_original_minimum_age_seconds = undef,
+  $establish_libvirt_service                  = true,
+  $install_libvirt                            = true,
   # DEPRECATED PARAMETER
   $libvirt_type                               = false
 ) {
@@ -127,17 +143,21 @@ class nova::compute::libvirt (
     }
   }
 
-  package { 'libvirt':
-    ensure => present,
-    name   => $::nova::params::libvirt_package_name,
+  if $install_libvirt {
+    package { 'libvirt':
+      ensure => present,
+      name   => $::nova::params::libvirt_package_name,
+    }
   }
 
-  service { 'libvirt' :
-    ensure   => running,
-    enable   => true,
-    name     => $::nova::params::libvirt_service_name,
-    provider => $::nova::params::special_service_provider,
-    require  => Package['libvirt'],
+  if $establish_libvirt_service {
+    service { 'libvirt' :
+      ensure   => running,
+      enable   => true,
+      name     => $::nova::params::libvirt_service_name,
+      provider => $::nova::params::special_service_provider,
+      require  => Package['libvirt'],
+    }
   }
 
   nova_config {